Measurement while drilling (MWD) involves evaluating the physical properties of the well environment in three-dimensional space while extending a wellbore. MWD is now standard practice in many drilling operations and usually involves digitally encoding data and transmitting this data to the surface as pressure pulses in the mud system.
A mud pulser periodically constricts the flow of drilling fluid inside the drill pipe to generate meaningful pressure pulses which are then transmitted to the surface. The data conveyed by these pulses is embodied in the temporal pattern of the pulses. These measurements include downhole temperature, pressure, near-bit spatial attitude as measured by inclination and azimuth, gamma ray count rate and other parameters.
Because of the fluid signal attenuation over a given length of drill pipe, a minimum pressure pulse height must be generated downhole for each specific set of well conditions in order for the pulses to be detected and decoded at the surface. In other words, the pressure drop across the mud pulser affects the ability of the mud pulser to create meaningful pressure pulses. Conventional methods of providing selected pressure pulse amplitudes typically require manually changing the diameters of the poppet and orifice components that constrict flow within the mud pulser tool. This conventional approach lacks precision, is time consuming and often leads to job failure due to improper sizing. Accordingly, there is a need for providing a mud pulser device that automatically adjusts to a selected pressure drop.